Breast pump systems are used for collecting breast milk expressed from a lactating woman. Some breast pump systems have a milk collection device with a funnel that fittingly receives the woman's breast. In many cases, a vacuum pump provides cyclical periods of positive and negative pressure to the milk collection device. During periods of negative pressure (subatmospheric pressure), vacuum delivered to the device withdraws a small discrete volume of milk from the breast and conveys that charge of milk to a small charging chamber. During each period of positive pressure, lightly pressurized air relaxes the breast momentarily and at the same time forces the charge of milk from the charging chamber to a larger milk storage chamber. The cycle repeats until the storage chamber is full or the woman is finished “pumping.”
Some breast pump systems have a milk collection device that is worn within the cup of a common brassiere. Examples of such systems are disclosed in U.S. Pat. Nos. 7,559,915; 8,118,772; and 8,702,646; all of which are incorporated herein by reference